1. Directions:
1. Read through the experiment, which looks at proving that a plant uses carbon dioxide (CO2) during photosynthesis.
2. Answer the questions on the last slide that follow the experiment.
.3 Place answers on a separate sheet of notebook and bring to class on Wednesday.

2. How can we show that plants use carbon dioxide in photosynthesis?

3. Hydrogencarbonate Indicator
Decreasing CO2 in indicator
Increasing CO2 in indicator
Atmospheric CO2 level
Hydrogencarbonate indicator is used to measure carbon dioxide levels in aquatic systems.
It is red in equilibrium with atmospheric air.
It becomes more orange/yellow with increased carbon dioxide levels.
It changes from red through magenta to deep purple as carbon dioxide is removed.

4. Method
1.Take four transparent containers that can be easily sealed.
2.Rinse the containers with a small amount of indicator.
3.Add a standard volume of indicator to each container and in three of the containers, place equal length sprigs of pondweed e.g. Cabomba
4.Seal all the containers.
5.Place one with pondweed into a dark cupboard.
6.Take another containing pondweed and cover it with shading.
7.Place the three remaining containers (including the one with no plant in), the same distance from a bright white light source and leave until there is a noticeable change in colour.
8.Make sure the lamp will not cause your pond water to overheat. You might want to place a transparent screen between the light and the plant, or a flat sided container of cold water to absorb the heat but none of the light.
9.When there is a noticeable change in colour in the indicator, remove the shading and compare the colours in the four containers to those in the picture.

5. Result in bright light

6. Result with thin shading

7. Result in dark

8. Conclusion: In which light setting was there less carbon dioxide?
Using your knowledge about photosynthesis, what is the rationale for a decline in the amount of carbon dioxide in that particular light setting?